The twoloop fiveparticle amplitude in N = 8 supergravity
Abstract
We compute for the first time the twoloop fiveparticle amplitude in N = 8 supergravity. Starting from the known integrand, we perform an integrationbyparts reduction and express the answer in terms of uniform weight master integrals. The latter are known to evaluate to nonplanar pentagon functions, described by a 31letter symbol alphabet. We express the final result for the amplitude in terms of uniform weight four symbols, multiplied by a small set of rational factors. We observe that one of the symbol letters is absent from the amplitude. The latter satisfies the expected factorization properties when one external graviton becomes soft, and when two external gravitons become collinear. We verify that the soft divergences of the amplitude exponentiate. We extract the finite remainder function, which depends on fewer rational factors. By analyzing identities involving rational factors and symbols we find a remarkably compact representation in terms of a single seed function, summed over all permutations of external particles. Finally, we work out the multiRegge limit, and present explicitly the leading logarithmic terms in the limit. The full symbol of the IRsubtracted hard function is provided as a supplementary file.
 Publication:

Journal of High Energy Physics
 Pub Date:
 March 2019
 DOI:
 10.1007/JHEP03(2019)115
 arXiv:
 arXiv:1901.05932
 Bibcode:
 2019JHEP...03..115C
 Keywords:

 Scattering Amplitudes;
 Supergravity Models;
 High Energy Physics  Theory
 EPrint:
 22 pages, 1 figure, 8 ancillary files